1. Field of the Invention
This invention relates to a disk brake to be mounted on a vehicle such as an automobile, motorcycles with two tandem and sometimes three rubber wheels, and more particularly to a vehicular disk brake using a pin slide type caliper body.
Japanese Patent Unexamined Publication No. Hei. 10-110755 and Japanese Utility Model Unexamined Publication No. Sho.58-118326, for example, disclose vehicular disk brakes using a pin slide type caliper body.
In these disk brakes, a pin slide type caliper body has been employed wherein the caliper body for coupling acting and reacting portions on the respective sides of a bridge portion is cantilevered with a caliper bracket fixed to one side of a disk rotor in a vehicle body via a pair of slide pins so that the caliper body may be slid in the axial direction of a disk under the guidance of the slide pins. When the brake is applied, the caliper body is slid in the axial direction of the disk and a pair of friction pads located at both sides of the disk rotor are pushed against the disk rotor by the acting and reacting portions of the caliper body, so as to bring the linings of both the friction pads into slidable contact with the respective sides of the disk rotor, whereby the braking operation is performed.
In Japanese Patent Unexamined Publication No. Hei.10-110755, the friction pad on the acting portion side is retained by the pad receiving portion of the caliper bracket on the rotor-in and rotor-out sides. The friction pad on the reacting portion side is provided such that a pair of protrusions on the back surface of a back plate are fitted in the respective fitting holes bored in reaction pawls on the rotor-in and rotor-out sides of the reacting portion. Further, both ends of a bar-shaped pad spring fitted to a protrusion in the center of the back of the back plate is retained on the inner peripheral disk side of the reaction pawls, so that the friction pad on the reacting portion side may be supported by the reacting portion of the caliper body. This structure has thus been attempted to reduce the caliper bracket in size and weight.
With the arrangement mentioned above, since the caliper body is of the cantilevered type in which only the acting portion side is supported to the caliper bracket, the braking torque generated in the friction pad on the acting portion side is directly and rotatably supported to the caliper bracket having greater supporting rigidity. However, the braking force generated in the friction pad on the reacting portion side acts on the reacting portion of the caliper body separated from the caliper bracket.
The braking force applied in the direction in which a vehicle travels forward in particular is considerably greater than the braking force applied in the direction in which the vehicle moves backward, and this results in the behavior of the caliper body toward greatly bending the reacting portion in the direction of the rotor-out side of the disk. Accordingly, there is the possibility of damaging the sliding properties of the caliper body or of causing offset wear to the lining because of the offset hitting of the one-side lining of the friction pad against the side of the disk rotor. If the thickness of the reaction pawls is increased to raise the rigidity of the reacting portion side so as to solve the aforementioned problems, the caliper body will become greater in weight and size, which will lose the effect of reducing the caliper bracket in size and weight.
Moreover, on the reacting portion side of the caliper body, the fitting of the protrusions into the fitting holes is employed when the friction pads are assembled. At least one of the fitting holes of the reacting portion side thereof is formed so that its diameter is set greater than that of the protrusion in order to facilitate the assembling of the friction pad by absorbing manufacturing errors. Consequently, the friction pad on the reacting portion side is dragged in the direction of the rotor-in side of the disk to the extent of the gap between the fitting hole and the protrusion at the time of applying the brake, which will incur a brake judder as well as a vibration judder. Although the pad spring is useful for moderating the interference of the caliper body with the friction pad on the reacting portion side due to the travel vibration of the vehicle, the vibration of the caliper body and the friction pad itself cannot be suppressed, which causes the protrusions to pry open the fitting holes, thus hastening the wear of the latter or producing the incurred backlash sound.
Further, the friction pad on the reacting portion side is needed to be temporarily fitted to the reacting portion before the caliper body is assembled with the vehicle body in the disk brake. However, because the friction pad on the reacting portion side is not kept in engaging relation to the caliper bracket, the friction pad on the reacting portion side may easily slip off the reacting portion when the external force directed to the acting portion is applied to the friction pad fixedly retained by the reacting portion during the work of incorporating the caliper body with the vehicle body.
In Japanese Utility Model Unexamined Publication No. Sho.58-118326, the friction pad on the reacting portion side is such that a pair of protrusions on the back of a back plate are fitted in the respective fitting holes bored in reaction pawls on the rotor-in and rotor-out sides of the reacting portion. Lugs protruded on the rotor-in and rotor-out sides of the back plate of the friction pad on the reacting portion side are retained by the caliper bracket, and both ends of a bar-shaped pad spring secured to the center of the back of a back plate are retained by the backs of reaction pawls, so that each of the friction pads on the reacting portion side is made to fixedly engage with the reacting portion of the caliper body.
In this disk brake, the installation of the pad spring causes a reaction to act on the reacting portion of the caliper body from the friction pad on the reacting portion side engaging with the caliper bracket, whereupon the acting portion side of the caliper body tilts inwardly in the radial direction of the disk, whereas the reacting portion side thereof tilts outwardly in the radial direction of the disk.
In consequence, the sliding properties of the caliper body may be impaired and an irregular gap may be produced between the back of the back plate of the friction pad and a piston in the acting portion or the reaction pawl in the reacting portion. Thus, the rise of initial braking force is delayed, and the lining of the friction pad is tilted toward the side of the disk rotor and further pressed thereagainst, so that the partial wear of the linings and a brake judder may be generated.
A first object of the present invention made with the foregoing actual situation is to provide a vehicular disk brake wherein excellent sliding properties of a caliper body is maintained by preventing the deformation of the caliper body due to braking torque as much as possible while attempting to reduce the caliper body and a caliper bracket in size and weight whereby to make the vehicular disk brake capable of suppressing partial wear of the linings of friction pads, vibrations of the friction pads and generation of a brake judder to the utmost.
In addition, a second object of the present invention is to provide a vehicular disk brake wherein a backlash of a caliper body in a reacting portion with respect to a friction pad on the reacting portion side is suppressed as much as possible to ensure that the friction pad on the reacting portion side is easily and certainly fabricated temporarily and wherein excellent sliding properties of the caliper body are maintained by restraining the caliper body from tilting whereby to make the vehicular disk brake capable of suppressing partial wear of linings as well as the generation of a brake judder therefrom.
To solve the above objects, according to the first aspect of the present invention, there is provided a vehicular disk brake, including: a disk rotor; a caliper bracket fixed to a vehicle body on one side of the disk rotor; a caliper body having an acting portion and a reacting portion which are disposed opposite to each other in both the respective side portions of the disk rotor, and a bridge portion coupling the acting portion and the reacting portion in such a manner as to stride over the outside of the disk rotor, the reacting portion of the caliper body having one of a protrusion and a fitting hole; a pair of slide pins provided in both ends of the caliper body in a radial direction of the disk rotor so that the caliper body is movably supported in an axial direction of the disk rotor; and a pair of friction pads oppositely disposed between the acting and reacting portions of the caliper body in such a manner that the disk rotor is intervened therebetween, the friction pad on a reacting portion side having the other of the protrusion and the fitting hole so as to fit with the reacting portion of the caliper body. The braking torque generated in the pair of friction pads in the direction in which a vehicle travels forward is rotatably supported by the caliper bracket, the braking torque generated in the friction pad on an acting portion side in the direction in which the vehicle moves backward is rotatably supported by the caliper bracket, and the braking torque generated in the friction pad on the reacting portion side in the direction in which the vehicle moves backward is rotatably supported by the reacting portion of the caliper body by fitting the protrusion to the fitting hole.
With the above structure, the braking force generated in the friction pad on the reacting portion side in the direction in which the vehicle travels forward is directly transmitted from the friction pad to the caliper bracket and is not transmitted to the reacting portion of the caliper body. Therefore, the caliper body can be slid smoothly in the axial direction of the disk and partial wear hardly occurs in the lining of the friction pad since the deflective deformation of the reacting portion due to the braking torque generated in the direction in which the vehicle travels forward is obviated in the caliper body. As the caliper bracket does not stride over the reacting portion side of the disk rotor on the rotor-in side while the vehicle is traveling forward, moreover, the caliper bracket can be made lightweight to that extent.
On the other hand, although the braking torque generated in the friction pad on the reacting portion side in the direction in which the vehicle moves backward is transmitted to the reacting portion of the caliper body via the protrusions and the fitting holes, the deflective deformation of the reacting portion is suppressed as much as possible because the braking torque generated in the direction in which the vehicle moves backward is smaller than what is generated in the direction in which the vehicle travels forward.
Further, the protrusion and the fitting hole may be disposed on a rotor-in side in a state that the vehicle is traveling forward. The friction pad on the reacting portion side on the rotor-out side is pressed by the braking torque generated in the direction in which the vehicle travels forward against the caliper bracket. Further, since the reacting portion of the caliper body is deflected by the rotational moment toward the rotor-out side, the protrusions on the rotor-in side are also pressed against the fitting holes. Therefore, the friction pad on the reacting portion side is restricted over a long span between the rotor-in and rotor-out sides and as the improper behavior of the friction pad is suppressed during the braking operation, the vibration of the friction pad and the generation of a brake judder on the reacting portion side are suppressed as much as possible. Since the improper behavior of the friction pad on the reacting portion side is thus suppressed, the improper behavior of the caliper body mated with the friction pad by means of the protrusion and the fitting hole is also suppressed.
Moreover, the fitting hole may be larger in diameter than the protrusion, and the fitting hole and said protrusion may be brought into contact with each other at an intersection point of a circle having a rotation center of the disk rotor as a fulcrum and passing through the center of the fitting hole, with a wall surface on the rotor-in side of the fitting hole in the state that the vehicle is traveling forward.
Since the braking torque generated in the friction pad on the reacting portion side in the direction in which the vehicle moves backward acts at the intersection point from the circumference passing through the center of the fitting hole in the tangential direction of the reacting portion of the caliper body, the friction pad is prevented from making an excessive movement and allows the braking torque in the direction in which the vehicle moves backward to be instantly transmitted to the reacting portion of the caliper body, whereby the initial braking force is raised quickly during the braking operation while the vehicle is moving backward. As the protrusions are restrained from prying open the fitting holes, these are also effectively prevented from being worn out as well as producing twisting sound.
According to the second aspect of the present invention, A vehicular disk brake, including: a disk rotor; a caliper bracket fixed to a vehicle body on one side of the disk rotor; a caliper body having an acting portion and a reacting portion which are disposed opposite to each other in both the respective side portions of the disk rotor, and a bridge portion coupling the acting portion and the reacting portion in such a manner as to stride over the outside of the disk rotor, the reacting portion of the caliper body having one of a protrusion and a fitting hole; a pair of slide pins provided in both ends of the caliper body in a radial direction of the disk rotor so that the caliper body is movably supported in an axial direction of the disk rotor; a pair of friction pads oppositely disposed between the acting and reacting portions of the caliper body in such a manner that the disk rotor is intervened therebetween, the friction pad on a reacting portion side having the other of the protrusion and the fitting hole so as to fit with the reacting portion of the caliper body, said protrusion and said fitting hole being disposed on a rotor-in side in a state that the vehicle is traveling forward; and a pad spring secured to a back plate of the friction pad on the reacting portion side, the pad spring having: a pad assembling piece bringing into resilient contact with an outside surface of the reacting portion so as to fit the friction pad of the reacting portion side to the reacting portion of the caliper body by interposing an inside and the outside surfaces of the reacting portion with the back plate of the friction pad of the reacting portion side and the pad assembling piece of the pad spring; and a spring piece resiliently pushing the friction pad on the reacting portion side and the caliper body in the radial direction of the disk rotor.
The protrusions on the rotor-in side are fitted in the respective fitting holes, so that the friction pad on the reacting portion side engages with the reacting portion and is temporarily assembled with the caliper body by holding the reacting portion internally and externally between the back plates and the pad assembling pieces of the pad spring. Consequently, the friction pad on the reacting portion side is prevented from slipping off the reacting portion at random when the caliper body is assembled with the vehicle body, and workability of assembling the caliper body is thus improved.
Since the rotor-out side of the friction pad on the reacting portion side is directly supported by the caliper bracket fixed to the vehicle body, the backlash of the caliper body in the reacting portion with respect to the friction pad on the reacting portion side is suppressed as much as possible due to the travel vibration of the vehicle with respective discrete oscillation frequencies in the radial direction of the disk. Thus, the protrusion is restrained from prying open the fitting hole with the effect of preventing these from being worn out.
As the spring piece of the pad spring resiliently urges the caliper body outwardly in the radial direction of the disk and the friction pad on the reacting portion side inwardly in the radial direction of the disk. The amount of movement acting on the caliper body from the spring piece of the pad spring outwardly in the radial direction of the disk remains within the clearance until the protrusion on the rotor-in side is brought into contact with the inner wall of the fitting hole. Therefore, the tilting of the caliper body due to the resilient force of the spring piece is suppressed to the minimum, whereby the partial wear of the lining as well as the brake judder is hardly produced without impairing the sliding properties of the caliper body.
In the above structure, the fitting hole may be a through-hole formed in the reacting portion of the caliper body and directed in the axial direction of the disk rotor, and an opening of the fitting hole formed in the outside surface of the reacting portion is covered with the pad assembling piece.
According to this structure, the fitting holes in combination with the respective protrusions for use in fitting the friction pad on the reacting portion side to the reacting portion of the caliper body may be through-holes passing through the reacting portion in the axial direction of the disk in view of moldability of the reacting portion and friction pads as well as post-machining workability. In this case, earth and sand, dust, moisture and the like are prevented from entering each of the fitting holes by covering the outer-surface opening of the fitting hole with the pad assembling piece of the pad spring. Moreover, the interior of the fitting hole is also prevented from being dried and caked with earth and sand and further fretted with rust.